In a network environment, in order to reduce bandwidth usage, server load, and data delivery lag, data may be temporarily stored (“cached”) by various types of systems, such as by intermediary server systems for use by client computing systems (“clients”) that are located near, or otherwise associated with, the intermediary servers. When a client submits a request for data (e.g., a Web page), the request may be routed to an intermediary server system that caches the requested data, which may then provide the cached data to the client. If the cached data has expired, the intermediary server may instead retrieve a current version of the data from a remote content data source and serves the current data to the client. However, various problems exist with such techniques.